Skip type check on unused parameters

I may be late, but I got stuck with the other solutions and this one work all the time for me:

function ({}={}, {}={}, {}={}, onlyThis) { console.log(onlyThis); }

comparison

When using the _0, _1, ... solution, I faced difficulties with scooped function like:

function parent(_0, _1, _2) {
  function child(_0, _1, _2) {
    // TypeScript crying about shadowed variables
  }
}

but with the empty object it work well:

function parent({}, {}, {}) {
  function child({}, {}, {}) {
    // :-)
  }
}

Even if the parameters are typed like:

function parent({}: number, {}: string, {}: any) {
  function child({}: number, {}: string, {}: any) {
    // :-) x2
  }
}

EDIT:

And as written here, setting a default value avoid error throwing if the given parameter is undefined or null.

function parent({}={}, {}={}, {}={}) {
  function child({}={}, {}={}, {}={}) {
    // :-)
  }
}

I was having the same problem. Using say express and routing you would often only want the res parameter.

router.get('/', function (req, res) { res.end('Bye.'); });

Your idea of using _ works here, but I've also found doing this works too.

function (_1, _2, _3, onlyThis) { console.log(onlyThis); }

This seems better, as only doing '_' I think might make using lodash/underscore a bit confusing, and it also makes it obvious it's the 4th parameter your interested in.

Update: It's been a long time since I posted this answer, and in the comments I'm getting a few miss conceptions. So though I would clarify.

Using the underscore trick is still very useful in Typescript. Like I mentioned in my original answer say if you was using express and did app.get('/', (req, res) => { you will get a warning 'req' is declared but its value is never read, but if you do -> app.get('/', (_req, res) => { the warning will go away. You should not get the error TS7006: Parameter 'req' implicitly has an 'any' type. error anyway, as @types/express should be implicitly typing this param anyway.

Update 2,. Please note the second answer here using {} for parameters, might look cool, but it's considerable slower, so personally I would be careful using inside tight loops.